Agricultural dehydrating system



g. n. ARNOLD 3,102,794

11 Sheets-Sheet 1 AGRICULTURAL DEHYDRATING SYSTEM Sept. 3, 1963 OriginalFiled Jan. 2, 195a IN V EN TOR. 658.4400. fiE/Vfll/D 4&4, M x KMArroe/vsvs Sept. 3, 1963 G. D. ARNOLD AGRICULTURAL DEHYDRATING SYSTEMOriginal Filed Jam 2, 1953 11 Sheets-Sheet 2 INVENTOR. szmcoD amma BY W,M r 41% ATTOENEYfi Sept. 3, 1963 s. D. ARNQLD AGRICULTURAL DEHYDRATINGsys'rm Original Filed Jan. 2, 1953 11 Sheets-Sheet 3 ml amok 66,544.02Hana 4.0

BY W, AM 44% Arroe/vsv Sept. 3, 1963 a. D. ARNOLD AGRICULTURALDEHYDRATING SYSTEM Original Filed Jan. 2, 1953 11 Sheets-Sheet 4 1N VENTOR. 652 440 0. Hen/04a AM/ Mr M A r702: Y5

Sept. 3, 1963 e. D. ARNOLD AGRICULTURAL DEI-IYDRATING SYSTEM OriginalFiled Jan. 2, 1953 11 Sheets-Sheet 5 INVENTOR. 652/4402 QQ/VOA-D BYm,m4m

ATTQENEY! P 1 G. D. ARNOLD 3, 102,794

AGRICULTURAL DEHYDRATING SYSTEM Original Filed Jan. 2, 1955 11Sheets-Sheetfi INVENTOR. I ll G-EeAmo 0. 143N040 e. D. ARNOLD 3,102,794AGRICULTURAL DEl-IYDRATING'SYSTEM original Filed Jan. 2, 1953 11Sheets-Sheet 7 Sept. 3, 1963 "1 kg INVENTOR. 65244.0 0 flea 04.0 BY MJI,M r

- ATTORNEY} Sept. 3, 1963 G. D. ARNOLD AGRICULTURAL DEHYDRATING SYSTEMOriginal Filed Jan. 2, 1953 11 Sheets-Sheet 8 INVENTOR. eaemcoD.Ale/104.0

BY AM, AI-Mr Sept. 3, 1963 Original Filed Jan 2, 1953 Wllilllllllllmlmlfi' a. D. ARNOLD 3,102,794

AGRICULTURAL DEHYDRATING SYSTEM 11 Sheets-Sheet 9 INVENTOR.eleaaoafle/vmo ATTORNEY} Sept. 3, 1963 s. o. ARNOLD AGRICULTURALDEHYDRATING SYSTEM Original Filed Jan. 2, 1953 11 Sheets-Sheet 1OINVENTOR. $52,440 0. B AM my 4&4,

Hie/V640 Arromvsvi Sept. 3, 1963 I e. D. ARNOLD AGRICULTURAL DEHYDRATINGSYSTEM Original Filed Jan. 2, 1953 11 Sheets-Sheet 11 WNW Nkm

INVENTOR. GEEQLD D. Hen 01.0 BY

United States Patent 3,102,794 AGRICULTURAL DEHYDRATING SYSTEM Gerald D.Arnold, Galesville, Wis.

Original application Jan. 2, 1953, Ser, No. 329,255, now Patent No.2,822,153, dated Feb. 4, 1958. Divided and this application Oct. 28,1957, Ser. No. 692,833

16 Claims. (CI. 3410) This application relates to an agriculturaldehydrating system. Included are improvements in the feeder, thefurnace, and the controls which automatically regulate the operation ofthe system as a whole and cooperate with the various improvements in thespecific parts thereof. The present application is a division of myapplication 329,255, filed January 2, 1953, now Patent No. 2,822,153,entitled Agricultural Dehydrating System.

The feeding arrangements include meanswhereby the material to be driedcan be delivered into the drier on one or more than one consecutivelyoperating conveyors, at least one of which is variable as to speed andautomatically regulated by the control system. Desirably included arecoacting sets of conveyors for assuring uniformity of flow of materialat whatever rate is determined by the control system.

The control system not only varies the rate of feed of the material intothe apparatus but varies the temperature and rate of flow of the air.For reasons hereinafter explained, the damper means heretofore proposedto be used for this purpose do not get the results herein sought and oneof the improvements in the furnace is to provide damper means which willnot only operate more effectively wtih the controls and the rest of thedehydrating system, but will operate to keep the furnace temperatures attheir adjusted values and to protect the furnace lining from injury.

The burner 0r burners are directed tangentially into a cylindricalfurnace chamber from which the outlet is also tangential and in the samesense of rotation as the gases. The outlet is axially remote from theburner so that the gases travel helically within the cylindrical furnaceand leave without any abrupt change of direction.

Dehydrating air (in addition to air admitted at the burner to supportcombustion) is admitted tangentially immediately in advance of theburners so that the flame from the burners is cushioned by a helicallymoving current of cooler air which shields the furnace lining from theflame. This auxiliary air is desirably not cold atmospheric air,however, having first been passed about the furnace jacket from theadmission dampers to the point of entrance in the furnace proper. Thereare one or more admission dampers opening into the jacket and whilethese are subject to a common control in accordance with the temperatureof outlet gases leaving the dehydrator, at least one of the dampers hasseparately controlled limiting means automatically set in accordancewith the humidity of the ambient air, thereby automatically achieving aregulation never heretofore possible to compensate for changes inhumidity.

Other dampers admit auxiliary air directly into the furnace dine and areso connected with the automatic control system as to operate inopposition to the dampers which admit air through the furnace jackets tothe furnace itself. This arrangement is useful primarily in shuttingdown the apparatus and it serves to keep the heat in the furnace,thereby avoiding the abrupt chilling of the furnace lining. This isparticularly useful when the shutdown is temporary, since it avoidscracking of the lining, at the same time virtually instantly cutting offthe flow of heat into the dehydrating drum.

In normal operation, the dampers for admitting air directly to the timeremain entirely closed and the air dampers controlling air admission tothe furnace remain in a manually adjustable, wideopen position except asmodified by the humidistat control to allowfor changes in humidity inthe ambient air. operate with high inlet temperature and low outlettemperature, the reduction in temperature being effected by evaporationof moisture from the material dehydrated. The rate of evaporation, andconsequent reduction of temperature within the drum, depends upon thefollowing factors, among others:

(1) The volume and velocity of the dehydrating gases.

(2) The extent to which the material to be dehydrated is distributed byshowering action across the entire cross section of the drum.

(3) The degree of vacuum within the drum.

d (4) The time required for material to go through the rum.

Opening the air admission dampers too widely will increase the velocityof flow of the dehydrating gases and will decrease the vacuum within thedrum. Both of these factors operate to reduce dehydrating action andthereby to reduce the differential between inlet and outlet temperaturesby decreasing the inlet temperature and increasing the outlettemperature with consequent waste of fuel and ineffective dehydration.On the other hand, if the air inlet openings are too far restricted, thematerial will be held in the drum for a longer time but the volume ofgas through the drum may be inadequate to carry out the moisture,thereby reducing the capacity or rate of dehydration. i

Still another control arrangement optionally used permits manipulationof the controls automatically in response to variation in moisturecontent of the material to be dehydrated. This feature is an alternativearrangement, there being opposed electrical contacts between which thematerial passes while confined under pressure, a delicate instrumentbeing used to measure the variation in current flow between the contactsaccording to the moisture content of the material, there being a controldevice whereby the movement of the pointer of this instrument effectsadjustment of the entire system, desirably lby manipulation of thetemperature control knob at the outlet thermostat in the same manner asthe knob might be controlled manually but for this automaticarrangement. This moisture testing device also regulates the dischargefan speed to maintain the correct volume of pneumatic current throughand vacuum within the drier drum at all times and which likewise mightbe controlled manually but for this automatic arrangement.

Alternatively the speed of the fan may be made responsive to themoisture content of the material to accelerate the flow of gases throughthe dehydrating drum. in proportion as the moisture content of theincoming material is higher. Increase of fan speed not only increasesthe volume of drying gas to which the material is exposed but it alsoincreases the vacuum in the drying drum, both of these factorsaccelerating dehydration without increase in the temperature of thedrying gases. Only if these measures fail to achieve complete,dehydration will the output temperature decrease to automatically effectan increase in the rate of burner operation to raise the temperature ofthe input gases.

Absolute accuracy in dehydration to a predetermined moisture content hasnever heretofore been achieved and is very important. If the dehydratedmaterial is not adequately dried, it may heat or spoil in storage; itmay be subject to loss of color and vitamin content; and it will bediflicult to grind or will require more power for grinding.

Because of the impossibility of achieving dehydration accurately to anyfixed standard in the use of prior art apparatus, it has heretofore beencommon practice to overdry some or all of the material in order toassure Desirably the drier should i that none of itwill be underdried.Over-dehydration in- 'rate of flow of the material and the rate of flowof thegases, as well as the volume of the latter. Another very importantfactor is the showering of the material across the stream of dehydratinggas. The showering is a 'relatively constant factor, whereas the otherfactors above mentioned are variable. Since the advance of the materialthrough the dehydrating drum is. dependent upon the increments ofadvance thereof effected by the gases in the course of each showeringaction, it will be evident that the greater the number of times thematerial is lifted and-dropped across the stream of gases, the morerapid may be its advance through the dehydrating drum. However, the rateof advance may be increased or decreased according to the velocity ofthe dehydrating gases. Automatic controls have heretofore dependedalmost exclusive ,ly upon the outlet temperature of the gases dischargedfrom the dehydrating drum. For many purposes, this temperature is asatisfactory criterion, since the initially hot gas is cooled only tothe extent that it has evaporated water vapor from the material to bedehydrated. Consequently, if the temperature of discharged gas rises, itmay means that an inadequate supply of material is being received or atthe burners are operating at too high a capacity or that the materialfed into the machine is already partly dry, etc.

One remedy heretofore proposed has been to have the outlet thermostatcontrol the rate of input feed of material to be dried and also controlthe burner and the air admission damper to reduce burner temperature andincrease the amount of air admitted in the event of temperature rise atthe outlet.- However, an increase in the amount of air admitted willaccelerate the flow of gas through the dehydrating drum and thereforeaccelerate the rate of movement of the material through the drum. Thiswill be contrary to what is actually needed in the event that the risein outlet temperature is due to an increase in the humidity of theambient air. Accordingly, I have provided, in the present invention, acam which limits the opening of the furnace dampers in accordance withambient air humidity. Cross reference is made to my Patent No.2,672,108, issued March 16, 1954, which was co-pending with myapplication Serial No. 329,255, filed January 2, 1953.

In the drawings: FIG. 1 is a general view in side elevation of adehydrating system embodying my invention.

FIG. 2 is an enlarged detail view partially in section and partially inside elevation of the feeder shown in FIG. 1.

FIG. 2A is a view similar to FIG. 2 showing a slightly modified feedingcontrol arrangement.

" FIG. 3 is an enlarged fragmentary detail view in side elevation ofportions of the feeding mechanism which 5-5 of FIG. 2.

FIG. 6 is a detail View taken in section on the line 66 ofFIG. 5.

FIG. 7 is a detail view taken in section on the line 7-7 of FIG. 6. 1

FIG. 8 is a fragmentary view partially in side elevation a and partiallyin longitudinal section showing the dehydrating drum on a larger scalethan in FIG. 1.

FIG. 9 is a view taken in section on the line 9-9 of FIG. 8.

FIG. 10 is an enlarged detail view of the furnace on the sectionindicated at 1010 in FIG. 11.

FIG. 11 is a transverse section through the flue pipe at the rear of thefurnace on the line indicated at 1111 in FIG. 10.

FIG. 12 is a view taken in section-on the line 1212 in 'FIG. 11. FIG. 13is a view taken in section on the line 13-13 of FIG. 10.

FIG. 14 is a view on a reduced scale taken in section on line 11414 ofFIG. 12. I

FIG. 15 shows the furnace in plan, partially broken away to a horizontalsection.

FIG. 16 is a view in horizontal section of a somewhat modifiedembodiment of the furnace.

FIG. 17 isa view in side elevation, partially broken away to the line17-17 in FIG. 18, showing on a reduced scale a further modifiedembodiment of the invention in which a furnace has a cylindricalcombustion chamber with a vertical axis.

FIG. 18 is a view taken in section on the line 1818 of FIG. 17.

FIG. 19 is a view taken in section on the line 19 -19 of FIG. 17.

FIG. 2:0 is a view in side elevation of damper controls for the furnace,the latter being fragmentarily illustrated.

FIG. 21 is another fragmentary view in side elevation of a dampercontrolling linkage.

FIG. 22 is a view partially in side elevation andpartially in sectiondiagrammatically illustrating the various thermostatic and hydnomaticcontrols of the material feed burners and dampers.

' FIG. 23 is a view taken in section on the line 23-23 of FIG. 22.

FIG. 24 is a view taken in section on the line 24-2 4 of FIG. 22.

FIG. 25 is a circuit diagram of the arrangement whereby a sensitiveinstrument may be used to control a motor having considerable power.

FIG. 26 diagrammatically illustrates an optional ar rangement wherebythe moisture content of the material to be processed may be used toadjust the control system.

FIG. 27 is a view diagrammatically illustrating a modification of thedevice of FIG. 26.

FIG. 28 is a view in longitudinal section through a modified feedingconveyor arrangement in which controls similar to those heretofore shownare here employed to control the functioning of a self-unloadingvehicle, the latter being illustrated in rear elevation.

FIG. 29 is a view in axial section through the blower E.

FIG. 30 is a diagrammatic view on a reduced scale and in longitudinalsection of the vehicle shown in cross section in FIG. 28.

The general organization of the dehydrator comprises a receiver A,feeding conveyor B, furnace C, dehydrating drum D, blower fan E, cycloneseparator F, blower fan G, and cyclone separator and bagger H, all asshown in FIG. 1.

The receiver A and many of its component parts are illustrated on sheets2 and 3 in FIGS. 2 to 7 inclusive.

.Referring'to FIG. 5, truckloads of produce to be dried can be driven upthe ramp 1 onto a platform 2 supported by beams 3 of such strength as tosupport the truck and its load. Operating over the platform is aconveyor 4 which operates sufficiently slow so that its cross slats 5can be forced beneath the truck wheels without being arrested thereby.The produce is dumped onto the platform 2, isdelivered rearwardly by theconveyor in the direction of arrow 6, and discharged onto an upwardlyinclined conveyor apron 7. In reaching this point, the

material passes below the lower guide sprocket 8 of a relatively fastmoving conveyor 9 which includes cross bars 10 having projecting fingers11 for loosening up the material and distributing it on conveyor apron7.

The material is discharged from conveyor apron 7 into the feed conveyortrough 12 onto the table 13, this being traversed by the upper flight 14of conveyor 15. The table 13 is substantially horizontal for the fullwidth of apron 7, as best shown in FIG. 2. Beyond such apron, theconveyor chains pass beneath guides 16 and the table extends upwardly atan incline as shown at 17. Material carried upwardly upon table portion17 by conveyor is leveled 01f to uniform depth by conveyor 18 which maycomprise an apron as best shown in FIGS. 2 and 4 provided withprojecting lugs 19 having a rearward rake with respect to the directionof conveyor movement indicated by the arrow 20. This conveyor operatesover pulleys 21 and 22 on shafts 23 and 24, respectively. A conveyorframe 25' connecting such shafts is pivoted coaxially with shaft 23 andcounterbalanced, externally of trough 12, by arms 26 upon whichcounterbalancing weights 27 are longitudinally adjustable as best shownin FIGS. 2, 3 and 4. This arrangement leaves pulley 22 floating, so thatit may readily rise when the produce accumulates beneath it in themanner indicated at 28 in FIG. 2. The resistance to upward movement ofthat end of conveyor frame 25 in which shaft 24 and pulley 22 aresupported will obviously depend on the position of the counterweights27. As will hereinafter be pointed out, I may use the pivotal movementof the conveyor frame, in response to accumulations at 23, to controlthe rate of operation of receiving conveyor 4 to the end that the feedof this conveyor will be retarded when excessive material accumulates onconveyor I15. Since all of the material on conveyor 15' must passbeneath pulley 21, and since this pulley operates on a fixed center, thematerial carried by conveyor 15 beyond its pulley will be reduced to asubstantially uniform level as shown at 29 of FIG. 2.

Instead of pulleys 21 and 22 and belt 18, the floating frame 25 maycarry the toothed rotors 21' and 22 as shown in FIG. 2A, the operationbeing similar to that above described.

At their upper ends, the chains 14 of conveyor 15 pass over sprockets 30on a shaft 31, as best shown in FIG. 12. The material is here dischargedto fall through hopper 32 into the rotary charger housing 33 in whichthere is a paddle type rotor 34 for delivering the material through port35 into [the flue pipe 36 which connects the furnace C with thedehydrating drum D. During dehydrating operations, the flue pipe 36 isfull of high velocity gases at high temperatures of the order of 1400 to1800" F. These gases are partly products of combustion and partly air.The heat is derived from the burning of fuel in the furnace C in themanner now to be described, reference being made to FIGS. 10 to 17.

The furnace may comprise an outer wall or jacket 40 and an inner wall 41lined with refractory material at 42. The refractory lining 42 may alsoextend into the flue 36 which extends tangentially from the combustionchamber 43 as best shown in FIG. 12. The combustion chamber is desirablycylindrical. Flue 36 may open from the center as shown in FIG. 11 andFIG. 15, or it may open toward one end as shown in the modifiedembodiments of FIGS. 16 and 17. In any case, if the flue 36 is circular,in accordance with conventional practice, it is expanded at its inlet36' (FIG. 13) into tangency for the full width of the flue in order topermit unimpeded flow of gases from the combustion chamber into theflue. But for such expansion, the flue would be tangent to thecombustion chamber wall only at a single point.

Conventional burners 44 are directed into burner pockets 45 which aresubstantially tangential respecting combustion chamber 43* and axiallyoffset from the flue through which the gases escape from such chamber.The direction of tangency of the burners is in the same sense ofrotation as the direction of tangency of the flue so that the productsof combustion discharged. tangentially into the chamber and therebycaused to rotate therein will pass helically through the chamber and outthe flue without any sharp change of direction. In the constructionshown in FIG. 10, the burner pockets 45 are in the back of the furnace,at the same side of its vertical center line as that from which the flueissues. In the construction shown in FIGS. 17 and 18, the burner pockets45' are at the opposite side of the furnace from the flue. Ordinarilythey Will be axially remote from the flue, as suggested in FIG. 17 butthe same helical flow of gases will occur in the combustion chamber,regardless of the specific location of the inlets and outlets.

Apart from the air supplied to the burners for the combustion of thefuel, drying air is admitted to the combustion chamber to be admixedwith the flue gas and heated (thereby, not only increasing the totalvolume of hot gas, but tempering the heat of the products of combustion.Some of the tempering and drying air is admitted through damper ports 47controlled by dampers 48 and located immediately beneath and above theflue 36 as shown in FIG. 11. The great majority of such air is admittedthrough three damper ports 49 controlled by dampers Stl, all mounted onthe same rock shaft 51 as shown in FIG. 12 and connected by links 52 and53 to operate in unison with dampers 48. All dampers are accurately setto a maximum open position ('which will vary for different products tobe dried) by a stop 52' (FIG. 20). If the damper opening is too large,fuel will be wasted; if too small, dryer capacity will be restricted.

All of the admitted air finds its way intothe jacket space 57 (FIGS. 10and 12.) and passes completely around the inner furnace wall 41 to aplenum chamber at 58 separated by partition 59 from the point ofadmission. From the plenum chamber 58, numerous ports 60 enter thecombustion chamber 43, desirably throughout the length thereof, as bestshown in FIGS. 10 and 13. The disposition of ports 60 is alsosubstantially tangential, but these ports are angularly oifset aroundthe periphery of combustion chamber 43 from the path of the products ofcombustion admitted through the burner pocket 45. Thus the atmosphericair, which has partially been heated by the outside of the wall of thefurnace in traversing the jacket space 57, tends to spread out as anannular cushion between the refractory lining 42 and the flame orproducts of combustion from the burners.

Since the air is much colder than the products of combustion and iswhirling in the same direction, there will be considerablestratification, the heavier cool air remaining interposed between thehot gases and the refractory lining. It has been found that this gives agreat deal of protection to the refractory material and substantiallycompletely protects it against fusing and cracking. However, as theproducts of combustion and the air leave the combustion chamber 43 andenter the flue, they are no longer whirling in stratified layers butbecome thoroughly intermixed to enter the dehydrating drum as asubstantially homogeneous stream of drying gases.

Inasmuch as it is quite difficult to line a horizontal cylinder withfire brick or other refractory material, there are substantialadvantages in a furnace in which the cylindrical combustion chamber isset on a vertical axis as suggested in FIGS. l7, l8 and 19. In such acase, the strong supporting wall previously required for the refractorymaterial can be wholly or substantially eliminated and the fire brickbecome self-supporting. It is a simple matter to lay up a cylindricalwall of fire brick in this device and to provide a crowned fire brickroof at 4-2. Even the jacket 40" may be made lighter in thisconstruction, since it is not obliged to provide support for anythingother than itself. In the construction illustrated, I use insulation 40retained by shell 40' about the refractory lining 42. The blanket ofcold air intervening between the products of combustion and therefractory lining makes it unnecessary to circulate cooling air aroundthe lining. Accordingly in this construction, the dampers t) admit thesupplemental air through passages 60' directly into the combustionchamber as clearly shown in FIG. 18. Due to these and other advantages,there are great savings of expense in erection of this furnace.

To illustrate the fact that the fine and inlet arrangement maynot beprecisely as shown in FIG. I have shown in FIG. 18 of the drawing analternative embodiment in which the burner pocket 45' tangentiallyenters the combustion chamber in the lower front portion thereof. Theair port damper 59 is unchanged except in location, being arranged toadmit air directly into the combustion chamber in a tangential directionthrough the ports 60 which open into the combustion chamber 43 near thebottom thereof.

Under'certain circumstances, it becomes desirable to increase the amountof air in relation to the amount of flue gas, or completely tosubstitute air for flue gas. To this end, the line pipe 36 is providedwith an inlet at 62 (FIGS. 10, 12 and 14), the inlet having largeadmission ports 63 at its opposite sides controlled by crossconnectedshutters or dampers 64 which operate in unison and desirably opposite tothe furnace inlet dampers above described.

The pressure differential which produces movement of the current ofgases through the line and the dehydrating drum results from theoperation of a powerful blower at the 'outlet of the drum. A substantialdegree of depression or partial vacuum exists within the dehydra-t-ingdrum as a result of the fact that the gases are circulated by suction atthe drum outlet instead of being subjected to super-atmospheric pressureat the dnum inlet. In addition to the fact that this partial vacuum inthe dehydnating drum assists in the removal of water vapor from theproduce which is being dehydrated, the arrangement facilitates thesealing of the connection between the fine and the drum, this beingeffected by a floating seal which atmospheric pressure holds to the endof the drum ias presently to be described.

The dehydrating drum as best shown in FIGS. 8 and 9, is desirably of thetriple pass type having an inner tube or shell 65, an intermediate shell66 and an outer shell 67. The inner tube or shell 65 is approximatelyconcentric with and spaced somewhat outside of flue pipe 36.

Arms 69 carried by the flue pipe (FIG. 8) support by means of chains 70a sealing ring 71 which may be made of metal or of brake lining materialor the like. The ring fi-ts closely to the pipe 36. By reason of thepartial vacuum existing within the dehydrating drum D, atmosphericpressure forces the sealing ring 71 against a flange 72 provided at theend of tube 65. It will be understood that the entire drurn D isrotatable. The bearing contact between the sealing ring 71 and flange 72readily permits this rotation and the suspension of the ring leaves itfree to move inwardly and outwardly in response to any irregularity inthe bearings and to accommodate any reasonable misalignment between thedrum and the inlet and outlet tubes.

The various tubes or shells comprising the drum D \are mounted in thegeneral organization disclosed in my Patent No. 2,618,865, grantedNovember 25, 1952. The riding rings 75, 76 are carried by pairs of rolls77, 78 mounted in suitable bearings as shown in FIG. 9. The ring 75 isconnected by gussets 79 with a semi-toroidal head 80 which is fixed bywelding-or the like to the outer shell 67 and the inner tube 65 at theinlet end of drum D, the inner tube 65 projecting beyond the head toreceive bearing contact with seal 71 as above de scribed.

At the other end of drumD, the inner tube 65 has a slip ring 81 fixed toit and this slides within an apertured ring 82 held to gusset 84 by apeg 83 integral with the gusset 84 anchored to the intermediate shell 66by bolts 85 which also pass through gussets 86- and gussets 87 from theoutside of drum D as also shown in FlG. 8. As the inner sleeve or shell65 expands and contracts, its one end is free for relative movement inring 82, its outer end being anchored to head at the end of the drum D.The inter-mediate shell 66 is anchored at the outlet end of dnum D bybolts which connect it to gussets 84 and 86-. It can expand and contractwithin a band 89 at the inlet end of drum D within which there is a slipring 90 fixed to the end of the intermediate shell, the shellterminating in spaced relation tothe semi-toroidal head 80 to leaveclearance for the passage of material from the inside around to theoutside of the intermediate shell.

Communication between the inner tube 65 and the space between that tubeand the inner shell is provided at the outlet end of the drum, suchcommunication taking place within an inner quarter toroidal drum head 92having a central closure 93. The material passes from left to right, asviewed in FIG. 8, through the inner tube, thence back through the innertube and the intermediate shell 66, thence from left to right betweenintermediate shell 66 and outer shell 67, finally being dischargedbetween head element 92 and head element 94- and head closure 95 intothe outlet pipe 96, the latter having an annular seal 97 engaged by headring 98 and held by atmospheric pressure to the head ring whilesupported from pipe 96 the same as the seal 71 already described.

The dehydrating drum B is provided with a sprocket 99o driven by chain99 from motor 100 (FIG. 1) for the rotation of the drum.

The outlet conduit 96 is connected by the trusteconical throat 101 withthe casing 102 of blower E. The outer wall of this casing is volute,leading to the tangential outlet 103 connected by pipe 104 to thecyclone F. A shaft 106 projects into the casing and carries a runner orrotor with arms 107 which support blades 108 desirably tapering in bothdirections from their mid-points as best shown in FIG. 29. It will beobserved that between the tapered margins 1139 of the blade-s and thetapered throat 101 of the inlet pipe 96 there is clearance for thematerial to enter casing 102 without being impacted by the blades. Theblades create a powerful vortex of the dehydrating gases and this vortexextends into the throat .101 and pipe 96 to an extent suflicient so thatthe solids are thrown out centrifugally to the periphery of throat 10-1and remain at the periphery of casing 102 well outside the path ofrotation of blade 108, being discharged tangentially through pipe 104without ever being touched by the blades. The construction of fan G issimilar but inasmuch as the two fans operate at different speeds, andrequire different power, each is provided with its own motor, the motorsbeing shown in FIG. 1 at 1 10 and 111, respectively. The fan E desirablyhas a variable speed drive to provide for adjustment of the rate of flowof dehydrating gases through the dehydrating drum, subject to manual orautomatic controls as hereinafter described.

The cyclones F and H are similar except in diameter, 7

cyclone F having the larger capacity because of the enormous volume ofdehydrating gases which it must handle.

The two cyclones also represent diiferent embodiments of back pressurecontrol means, but in each case the cyclone is designed to provide ameans for varying the discharge gases in accordance with variations inbarometric pressure in order to free finely powdered material from thegases with maximum efficiency, the manner in which this is done beinghereafter explained. The means of controlling flow of gas from thecyclones is interchangeable.

Pipe 104 discharges tangentially into the cyclone F in a conventionalmanner to establish a separation vortex tained with accuracy,

with the cyclone. The whirling mass of gas and solids moves helicallydownwardly through the cylindrical portion 113 of the cyclone into thetapered lower portion 114 thereof. At some point in the latter portion,the gases at the inside of the vortex will cease their downward movementand commence to move upwardly to escape through the gas outlet 115.

Despite the fact that the dehydrating gases have been cooled markedlywithin the separator drum, from a temperature of about l400 F.-1800 F.to a temperature of about 200 F.-300 'F., the material which has beendehydrated and which, by giving up its moisture, has effected thiscooling, is still rather hot upon discharge from separator F. In orderto reduce it as nearly as possible to atmospheric temperature, Idesirably cool it by reentraining it in atmospheric air in chamber 161(FIG. 1). This chamber has an inclined chute 16 2 in its bottom whichcommunicates openly at 163 with the atmosphere. Any stones or otherforeign matter will tend to fall through the opennig 163 in oppositionto the stream of atmospheric air drawn into such opening by the blowerG. The dehydrated produce will readily be entrained in the current ofair and will pass through blower-G without contact with its vanes.

The device as herein disclosed desirably includes a perfected system ofautomatic controls. These lower the cost of operation, increase theefficiencsy and insure the production of a more perfect and uniformlydried product by positive and automatic control of (a) the input ofmaterial into the drier; (b) the supply of fuel and combustion air tothe burners; (c) the temperature of the pneumatic current of dehydratinggas; (d) the volume and velocity of the current of dehydrating gas, andconsequently the time for which material to be dehydrated will beexposed to the gases within the drum; and (e) the point at whichseparation is achieved in the cyclones, thereby compensating .forchanges in barometric pressure. The various controls by which regulationis automatically achieved are operated thermostatically,humidistatically, barometrically and in accordance with the moisturecontent of the incoming product. Some of these controls have alreadybeen described, but the effect thereof and their cooperative action willhere be correlated with the remainder of the controls,

In my Patent 1,988,677 of Ianuary 22, 1935, I described means whereby athermostat exposed to the gases leaving a dehydrator drum could be madeto regulate the speed of an input conveyor generally corresponding tothat here illustrated at B, as well as the rotary charger for deliveringthe material from some such conveyor into the flue leading to the drum.The present device uses a thermostat at 290 in the outlet pipe 96 fromdehydrating drum D to control the rate at which the motor 291 drivesthrough chain 292 (FIG. 12 and FIG. 22), the rotary charger at 33 andthe sprocket 30 of the infeed conveyor '15. While automatic regulationof the infeed conveyor and charger was described in the patent aboveidentified, it never went into general use for lack of ancillarycontrolled devices, such as those hereinafter described, and includingmeans for rendering substantial- 1y uniform the amount of materialcarried by conveyor '15 at various points along its length.

As has already been explained, it is very desirable to be able to holdthe dehydrated material with accuracy to any predetermined moisturecontent. If the material is excessively dehydrated, it is not only ofinferior quality but it has consumed an excessive amount of heat andpower in dehydration. However, if it is unduly moist, the material willspoil. Therefore, in devices in which the moisture content at the outputcould not be mainit has been necessary to dehydrate the materialexcessively so that no portion thereof would remain sufliciently moistto spoil it.

In the device of my former patent, it was found inadequate to merelyaccelerate or decelerate the rate of operation of the infeed conveyor inaccordance with-the rise or fall of temperature at the dehydratoroutlet. If the rise was excessive, an immediate introduction ofadditional material was required in order that evaporation of themoisture therefrom might lower the dehydrator temperature; otherwise thematerial in the dehydrating drum might catch fire or at least becomescorched. Unless the amount of material at all points along the infeedconveyor could be maintained substantially constant, the amount ofmaterial supplied in response to an increase in the rate of conveyoroperation would not bear any predetermined relation to the outlettemperatures of the gases used in dehydration. There might be a. demandfor an increase in the amount of material but if the input conveyor wasunderloaded, a mere acceleration of the conveyor would not supply therequired material.

Accordingly, the present device combines with thermostatically regulatedconveyor speed control a further control for assuring the maintenance ofa substantially uniform layer of material on the infeed conveyor.

The pivotally mounted frame 25, counter-balanced by weight 27 on arm 26as shown in FIGS. 2, 3 and 4, and above described, has its driving shaft23 connected with motor 295 for the actuation of levelling conveyor 18,or

the alternatively usable rotors 21, 22 in the direction indicated by thearrows in FIGS. 2. and 2A. The conveyor flights 19in FIG. 2 and thefingers with which the rotors 21, 22' are provided in FIG. 2A serve topull rearwardlyon the elevator 15 all material in excess of thepredetermined depth shown beyond the levelling devices in FI G. 2.

Any excess of material building up at 28 beneath the free floating endof the levelling frame 25 oscillates the levelling frame clockwise asthe material accumulates. Any such oscillation is used to reduce therate at which material arrives at this point. For this purpose, motionof the levelling frame is communicated through link 296 ('FIG. 3) to acontrol lever 297 which operates the control valve 298 to admit a lesseror greater amount of compressed air from pipe 299 to pipe 300.

Pipe 300 leads to a pressure operated speed regulator 301 (FIG. 6). Thespeed regulator 301 adjusts the variable speed driving mechanismindicated at 302 and through which the motor 303 drives chain 304 whichactuates shaft 305 carrying the driving sprocket 306 for the loadingconveyor 4. Thus, if the supply of material accumulating at 28 behindthe levelling conveyor 18 decreases, conveyor 4 will be accelerated. Ifthe reserve material increases, conveyor 4 will be decelerated. Sincethe supply of material 011 conveyor 4 is by no means uniform, the massaccumulated at 28 beneath the floating end of conveyor frame 25 servesas a reserve from which the level on the infeed conveyor 29 isequalized.

The conveyors 7 and 9 are driven at a rate which may be constant bymotor 307 through sprocket 308, chain 309 and the driven sprockets 310and 311 on the drive shaft 8 for conveyor 9 and the drive shaft 312 forconveyor 7. Because of the equalizing effect above described, it is notnecessary to have the conveyors 7 and 9 partake of the speed variationemployed in driving conveyor 4.

An alternative feeding arrangement is shown in FIG. 28. The conveyor 15traverses table 13 in feed trough 12 substantially the same as in thepreviously described embodiments. The levelling devices of FIGS. 2 or 2Amay be used, that of FIG. 2A being illustrated. As the lever 25oscillates in response to accumulations of material (or the lackthereof) beneath rotor 22 at its floating end, pressure from the supplyline 299 is communicated at a greater or lesser value to the pipe 300which, in this instance, leads to a control 365 on a speed changer 366driven by motor 367 to operate a flexible shaft 368 detachably connectedwith the shaft 369 which serves as a Windlass upon which ropes 370 arewound to propel the follower 371 of a self-unloading vehicle which ismerely diagrammatically illustrated at 372, it being un derstood thatany self-unloading vehicle may be used at this point. In order thatdelivery from the vehicle may be rendered uniformly responsive to therate of advance of the follower 371, the vehicle is desirably providedwith a conveyor 373 extending upwardly and inwardly from the rear end ofthe vehicle, the upper end of such conveyor desirably being adjustablyfloated. A spring 374 exerts a forward bias on the upper end of thepivoted carrier 375 upon which the conveyor sprockets 376 and 377 aremounted. A rope 378 fastened over pulley 379 to a Windlass at 380permits the operator to draw the upper end of carrier 3 75 toward avertical position, in which position the conveyor functionssubstantially as a tail gate for the vehicle. When lowered and set inmotion by supplying current to motor 382, this conveyor tends to effectthe regulated discharge of the material by ejecting it uniformly as itarrives, so that the delivery of material into the trough will, inactual practice, depend upon the rate at which the follower 371 movestoward the rear end of the vehicle under the control of the floatinglever 25 as above described. In this embodiment, as in the previouslydescribed device, the objective is to accomplish uniformity of flow ofthe infeed conveyor B leading to the dehydrator.

Means is provided for utilizing variations of temperatures at the outletof the dehydrator to effect adjustments whereby material traversing theapparatus can be dehydrated to a predetermined moisture content.

As best shown in FIG. 22, an adjustment is provided by knob 315 for thecontrol valve 316 operated by thermostat 290 in the drum outlet pipe 96.This regulating knob at 315 permits the valve to be adjusted to respondto a [given extent at different temperatures to which the thermostat 290is subject, thereby enabling the moisture content of the materialdischarged from the dehydrator 'to be maintained at differentpredetermined values.

Valve 316 is located in the air pressure line 317 to control the ratechanging pneumatic motor 318 as described in my former patent.

The fluid pressure transmitted by such valve, as controlled by thethermostat (modified by the setting of knob 315) is also admitted tosimilar pneumatic motors at 319 and 320 which regulate the fuel supply(here represented by burner 44) and the air admission dampers 50 whichadmit the air to the combustion chamber to cushion the walls thereoffrom the heat of the flange, such air being mixed with the products ofcombustion to comprise the dehydrating gas used in the drum Pneumaticmotor 319 operates the dampers 64 which admit auxiliary air to the inlet62 which leads into flue 36 between the combustion chamber and the drum.

The damper motor 320 is connected to rock shaft 54 which directlyeffects the, regulation of the burners 44. The dampers 48 and 50, alloperating in unison also receive motion from rock shaft 54, through arm55 which has a pin 55' at its free end moving in a slot in link 56.

The damper rock shaft 51 has attached thereto an arm 56' to which ispivoted the link 56. The burners respond directly to automaticregulation by motor 320 while. the last motion provided by the slottedlink 5 6 permits damper response to lag for effecting control subsequentto burner response.

The controls already described are calculated to maintain the inflow ofmaterial and the inflow of dehydrating gases at substantiallypredetermined relative values. However, 'for complete accuracy, furtheradjustments must be made according to the initial moisture content ofthe material to be dehydrated and the humidity of the ambient airadmitted to the furnace.

If the water content of the ambient air, as determined by thehurnidistat diagrammatically illustrated in FIG. 22, is relatively high,the dampers 50 should be controlled in their movement so that they willnot operate through the same rangev as if the moisture content wereaverage.

In the device shown in FIG. 22, a-wet bulb thermostat 325 and a dry bulbthermometer 326 respectively com municate with bellows 327 and 328, therelative expansion of which operates the dampers through the mechanismshown. Bellows 327 acts on one end portion 329 of a bell crank 34%), thefulcrum 341 of which is mounted on bellows 328. The free end 342 of thebell crank is connected by link 343 with a floating lever 344, the linkbeing subject to the bias of tension spring 345. The lever 344 carries adouble contact at 350 which, according to the direction of leveroscillation, engages contacts 351 or 352, these being carried on the arm353 of a worm wheel 354 coaxial with the fulcrum of lever 344. Ifrelative humidity increases, the differential between the wet and drybulbs will be reduced, lever 340 will oscillate counterclockwise and acircuit to contact 352 will be closed. If humidity decreases, lever 340'will oscillate clockwise and the circuit to contact 351 will be closed.

The contacts 351 and 352 are connected to a motor 355 to operate themotor in forward or reverse direction, thereby driving the shaft 356 onwhich a worm 357 meshes with worm wheel 354. At its other end, the shaft356 carries a cam 358 in the path of a rocker am 359 carried by dampershaft 35. Thus, according to the humidity of the ambient air, the cam358 regulates the opening of the dampers 50 to maintain them open morewidely when humidity is low than would be the case if the humidity werehigh. This, in turn, regulates volume of how of dehydrating gas so thatunder high humidity conditions higher temperatures of dehydrating gasesat the drum inlet and reduction in rate of flow compensate for theslower dehydration under such conditions.

it will be observed in FIG. 22 that the cam 358 is mounted to be axiallyslidable upon shaft 356 subject to the bias of compression spring 361which urges the clutch jaw 362 on the hub of the cam into engagementwith the complementary clutch jaw 363 carried by shaft 356. Thisarrangement permits manual operation of the cam independently of thecontrol mechanism to any desired position, such adjustment beingprimarily intended for calibrating the apparatus to assure that thedamper position as fixed by the cam will reflect accurately the humidityconditions to which the control mechanism responds. It may be noted inpassing that similar provision for calibrating adjustment is made in allof the automatic controls.

Where any special situation requires in difierent apparatus, theelectrical connections to the reversible motors 355 (FIG. 22) may beinterchanged, it being my purpose to claim broadly the feature ofhumidity-control of air admission dampers in a dehydrating system.

In order to render the operation completely automatic, it is desirableto take account of the wetness of the material to be dehydrated, as wellas the humidity of the air used in the dehydrating gases. To this end, Ihave devised means responsive to the electrical conductivity of theincoming material, such conductivity being proportional to its moisturecontent, to adjust the apparatus to compensate for variations in suchcontent. Referring to FIG. 26, I have provided near the delivery end ofinfeed conveyor run 15 a pair of electrodes 390, 391. Electrode 390 issupported by insulation 392 in the bottom of the conveyor trough, whileelectrode 391 is supported by insulation 393 upon a lever 394 mountedfor pivotal movement on a rock shaft 395 which carries, externally ofthe conveyor trough a rocker arm 396 biased downwardly by a weight 397whereby material moving upwardly with conveyor run 16 is subjected topressure between electrodes 390 and 391.

An upwardly projecting arm 3% on rock shaft 395 is engageable with astop 399 to define a lowermost position of lever 394 which precludesdirect contact of electrode 391 with electrode 390 when there is nomaterial interposed between the electrodes. Short of such lowermostposition, the finger 400 on arm 398 opens a normally closed switch 401in the circuit to motor 402. Such circuit may also be opened by anothernormally closed switch 403 in series in such circuit with switch 401.Switch 403' is actuated by a governor-controlled arm 40 4 to open thecircuit when the motion of conveyor sprocket 405 ceases. The shaft 406of governor 407 is geared to sprocket 405 so that in the event ofshutdown of the conveyor, the circuit to motor 402 is opened.

Assuming that the conveyor is in operation and material to be dehydratedis present between the electrodes 390 and 391, any increase or decreasein the current flowing through the electrodes operates motor 402 in onedirection or the other as will now be described.

Connected in series with the electrodes and with a line 409 is asensitive volt meter 410 having a pointer 411 carrying electricalcontacts 412 at its end. Worm wheel 413 mounted substantially coaxiallywith the meter pointer 411 carries an arm 414 having spaced contacts 415and 416 between which the contact 412 of the meter pointer is normallycentered. If the meter pointer closes the circuit to either of thecontacts 415 or 416, the motor 402 is energized and drives worm 418 toactuate the gear wheel 413 in a direction to re-center contact 412between contacts 415 and 416, thereby breaking the motor circuit.

The same motor operation which re-centers the contact, actuates anotherworm at 419 engaged with worm wheel 420 which is connected with theadjusting element 315 of thermostat 290. It will be remembered that inthe construction previously described the thermostatic adjustment wasmade by manually operated knob at 3 The present arrangement mechanicallyactuates the control 315' to permit fluid pressure to flow through thevalve 316 in greater or less degree with the same result as if the knob315 had been manually operated to meet the exact requirements caused byincrease or decrease in moisture content of the supplied material. Thefluid supply line 317 is connected through valve 316 as shown in FIG. 22to control the various motors 318, 319, 320, for adjusting the dampers,accelerating or decelerating the infeed conveyor run 15, and controllingfuel flow to the burners through valve 425. In the oil supply line 424to the burner is a solenoid-opened spring-closed valve 425 (FIG. 22),held open electromagnetically when the burner is operating properly. Anormally closed switch 426 in an electric circuit including supply lineand the solenoid, holds the valve open. When the dampers 50 close totheir extreme position, rocker arm 427 on rock shaft 360, engages andopens switch 426 to close the valve 425 in oil line to shut down theburners. Consequently, if the current fails or the control capacity ofthe apparatus is exceeded in a direction calling for heat, the burnerwill be shut off to avoid destruction of the furnace.

In manual operation, if the arriving material supplied by the infeedconveyor increases in moisture, the operator normally re-sets thethermostat to allow for increased output temperature at the delivery endof the dehydrator. This readjustment of the thermostat results in theincreased supply of fuel and combustion air to the burners. Theautomatic adjustment of the thermostat through the arrangement shown inFIG. 26 accomplishes the same result but includes safety controls topreclude overheating in the event that the infeed conveyor stops ormaterial ceases to be supplied thereon, or in the event that the furnacetends to overheat.

In manual operation, if the material supplied for dehydration is lessmoist, the operator reduces the amount of heat or feeds more material.The automatic controls above described do the same thing mechanically.

FIG. 27 shows an alternatively or simultaneously usable arrangement inwhich I may change the speed of the exhaust fan E to increase the vacuumand accelerate air flow through the dehydrator when the material is Wetand heavy, the air flow being correspondingly reduced in speed when thematerial is dry and relatively light. To this end, the electrodes 3'90and 391 are connected to a control device at 430 which is comparable tothe control device shown in detail in FIG. 26, The output shaft 431corresponds to the shaft upon which Worm wheel 420 is mounted in FIG. 26and it is connected by link '432 with a variable pressure reducing valve433 which controls transmission to line 434 of fluid pressure to adamper motor 435 similar to the pressure-operated motors alreadydescribed. The motor 435 is connected to a speed changer 436 interposedbetween the fan motor and the exhaust fan E to vary the rate ofoperation thereof in the manner already set forth.

An increase in current flow between electrodes 390 and 391 will reflectincreased wetness of the material. This is cared for mechanically andautomatically through the disclosed apparatus by increasing fuelconsumption and increasing the speed of operation of the fan.

While it is not essential to the invention, I prefer to provide meanswhereby the operator can check upon the functioning of the entire ystemby consulting the instruments on one conveniently located control panel450. FIG. 1 diagrammatically illustrates this panel disposed adjacentthe furnace C (FIG. 1). By way of example, I have shown grouped on thepanel 450 a thermometer at 451 which shows temperatures at the outletfrom the dehydrator drum D, a pyrometer at 452 which shows temperaturesof the dehydrating gases at the point at which these leave the furnaceC, a humidistat dial at 453 which gives readings of relative humidity, amanometer at 454 connected to the interior of the drum to show thedegree of vacuum maintained therein by the exhaust fan E, a barometer at455 which shows atmospheric pressures, and a pressurestat 456 connectedto the operating line to show the air pressures therein available foroperating the various controls as above described.

In recognition of the importance of continuous uniform dehydration toassure adequate drying of the material while at the same time protectingagainst fuel wastage, scorching and under-drying while, at the sametime, making it unnecessary to employ the constant attention of skilledoperators to anticipate the various requirements for these purposes, Ihave provided a device which affords a continuous even flow of materialto be dehydrated and has controls which are self-adjusting in accordancewith changes in the moisture content of the material, and changes in themoisture content of the A major source of difliculty in connection withthe operation of previously known dehydrators has involved the shuttingdown of the apparatus and unloading the drum without injury to thematerial being dried, without overheating the drum, and without eitherwasting heat or injuring the furnace.

The present device provides controls such that when the feeding ofmaterial is stopped, whether at the conclusion of a given period ofoperation, or because of lack of material supply or because ofmechanical failure, the drum will automatically be completely unloadedwithout injury to the material or equipment. Stoppage of material flowresults in a rise in outiet temperature and will automatically reducethe fuel supply in proportion to any tendency of rise of temperaturewithin the drum, similarly the air required for combustion is reduced,this being controlled with fuel. The by-pass dampers on the furnace flueieading to the dehydrator drum will automati'ca-lly open; the damperscontrolling the admission of air to the furnace will close (if theseremained open, they would cool the furnace too rapidly); and finally, ifthe condition persists, the air and fuel supplied to the burners willultimately be completely shut olf. The bypass dampers will remain opento admit atmospheric air into the dehydrating drum until the current iscut off, whereupon they are automatically selfaclosing. The result ofthese several operations is to maintain within the drum the temperaturesappropriate for dehydration of such material as is passing therethroughuntil such material is completely discharged, at which time, the iack ofevaporation within the drum will create outlet temperatures such as toshut down the furnace as above described. It will be observed that thisis accomplished with full protection to thenfurnace, as well as thematerial in the At the same time, the exclusion of atmospheric air fromthe furnace during shutdown leaves the interior of the furnace hot tofacilitate immediate results of dehydration in the event that theshutdown was inadvertent.

I claim:

1. In a dehydrating system, the combination with a dehydrating drumhaving a dried material outlet, of means for supplying continuously tothe drum material to be dehydrated, means for supplying gases incontrolled volume and temperature to said drum for the dehydration ofsuch material, means for rotating the drum, the drum being providedinternally with flights for lifting the material and successivelyshowering it across the path of dehydrating gases moving through thedrum [to be advanced through the by such gases, moisture responsivemeans exposed to the moisture content of material prior to its admissionto the drum, and means controlled by said moisture-responsive means forvarying the dehydrating action of such gases on said material.

2. The device of claim '1 in which said varying means comprises a fanfor exhausting such gases from the drum provided With a variable speeddrive and means connected with said moisture-responsive mean-s foraccelerating the fan as the moisture content of such material increasesand for decelerating the fan as the moisture content of such materialdecreases.

3. The device of claim 1 in which the means for varying dehydratingaction comprises a thermostat exposed to dehydrating gases leaving thedrum, means adjustably controlled by the thermostat for regulating thetemperature of dehydrating gases admitted to the drum and an operativeconnection from said moisture-responsive means to said adjustablycontrolled means comprising means for effecting an increase of thetemperature of admitted dehydrating gas in relation to the temperatureof such gas at it leaves the drum proportionate to the moisture contentof the material approaching the drum, and for decreasing the relativetemperature of dehydrating gas admitted to the drum as the moisturecontent of such material decreases.

4. In a dehydrating system, the combination with a dehydrating drum,means for supplying dehydrating gases thereto at controlled temperaturesand in controlled volume, and means for supplying to said drum thematerial to be dehydrated therein, and means for regulating the rate atwhich such material is supplied, of means including a moistureresponsive instrument exposed to said material prior to its entry intothe drum and further including means connected with said instrument forvarying the dehydrating action of such gases on said material in saiddrum according to the initial moisture content of the material assupplied, and means for varying the said controlled temperature of thegases according to the moisture content thereof.

5. In a dehydrating system which comprises, a dehydrating drum having aninlet at one end and a discharge opening at the other end and providedinternally with flights and mounted for rotation, means for supplying tothe end of said drum the material to be dehydrated and heated gases fordehydration thereof, and an exhaust fan at the discharge end of the drumfor withdrawing the gases and material from the drum and effecting adehydratingcurrent of such gases longitudinally of the drum and acrosswhich the material to be dehydrated is repeatedly showered by saidflights as the drum rotates, the advance of the material beingproportioned to the velocity of the current inrthe drum and the degreeof the dehydration of the material, the combination with said fan of avariable speed drive for said fan whereby to control the velocity ofsuch current and the consequent extent to which material will beadvanced longitudinally of the i5 drum in each showering actionaforesaid, means for electrically measuring the moisture content ofmaterial supplied to the drum for dehydration, and means controlled bysaid moisture measuring means for automatically varying the speed ofsaid exhaust fan.

6. The device of claim 5 in further combination with a furnace forheating the dehydrating gas in advance of the admission thereof to thedrum, a thermostat exposed to the dehydrating gas adjacent thedehydrating drum outlet, and means controlled by the thermostat forvarying the temperature of the dehydrating gas admitted to the drum in adirection to compensate for increase or decrease in the temperature ofdischarged gas.

7. In a dehydrating system which comprises a dehydrating drum having aninlet at one end and a discharge opening at the other end and providedinternally with flights and mounted for rotation, means for supplying tothe end of said drum the material to be dehydrated and heated gases fordehydration thereof, an exhaust fan at the discharge end of the drum forwithdrawing the gases and material from the drum and effecting adehydrating current of such gases longitudinally of the drum and acrosswhich the material to be dehydrated is repeatedly showered by saidflights as the drum rotates, the advance of the material beingproportioned to the velocity of the current in the drum and the degreeof the dehydration of the material, the combination with said fan of avariable speed drive for said fan whereby to control the velocity ofsuch current and the consequent extent to which material will beadvanced longitudinally of the drum in each showering action aforesaid,a furnace for heating the dehydrating gas in advance of the admissionthereof to the drum, a thermostat exposed to the dehydrating gasadjacent the dehydrating drum outlet, means controlled by the thermostatfor varying the temperature of the dehydrating gas admitted to the drumin a direction to compensate for increase or decrease in the temperatureof discharged gas, and a variable speed feeder constituting a part ofsaid material-supplying means, thermostat-controlled means for varyingthe speed of said feeder for the increase and decrease thereof incompensation for increase and decrease of temperature or dischargeddehydrating gas, the connections between said thermostat and the meansfor controlling inlet gas ternperature including means for varying theinlet gas temperature only upon failure of the variation in the speed ofsaid feeder to compensate for changes in outlet gas temperatures.

8. A dehydrator comprising the combination with a dehydrating chamberhaving a material inlet, a material outlet, and means for supplying andmeans for exhausting dehydrating gas, of material-feeding means having avariable speed drive, dehydrating gas heating means having means fortemperature regulation, controlling devices comprising a device in thepath of material on said material feeding means and responsive to themoisture of material delivered by said feeding means, a deviceresponsive to the temperature of exhausted gases, and means controlledby said devices for correlating the speed of said feeder and thetemperature of admitted gases in accordance with the moisture ofadmitted material and the temperature of discharged gases to maintainsubstantially uniform dehydration of such material in said chamber in acontinuous operation.

9. The device of claim 8 in further combination with a means foradmitting ambient air in admixture with the dehydrating gases, meansresponsive to the relative humidity of such air, and means forcontrolling the relative amount of air admitted to such gases in inverseratio to its humidity.

10. In a dehydrating system of the type including a ro tatable drum, arelatively stationary pipe, and means for evacuating gases from saiddrum; the combination with such a pipe and a drum having a bearingsurface substantially concentric with the pipe, of a sealing'diskpositioned for bearing engagement with :the surface and having anaperture fitted about said pipe and means supporting said disk formovement axially of the pipe to and from engagement with the bearingsurface of the drum, said disk being free of bias and floating on saidpipe to be held against said surface by differential pressuresoccasioned by the evacuation of said drum.

11. The device of claim 10 in which the pipe is provided with a fixedsupport, said disk having a marginal flexible connection with saidsupport to be suspended therefrom to accommodate its movement to andfrom said surface along said pipe.

12 A method of dehydration which comprises the steps of exposingmaterial to be dehydrated to a dehydrating gas comprising thecombination of fiue gas and ambient air, establishing a current of suchgas, repeatedly showering such material transversely of the current tobe advanced by the current and supplying additional material to suchcurrent at a rate proportioned to the temperature of gas which has actedon such material, increasing and decreasing the speed and temperature ofsaid current of dehydrating gas in accordance with the increase anddecrease of wetness of the material to be dehydrated, and deceleratingsaid current in proportion to the rise of humidity in the ambient airadmitted thereto.

13. A method of dehydration which comprises the steps of establishing acurrent of dehydrating gas, delivering through said current particles ofmaterial to be dehydrated to a predetermined moisture content, sensingthe moisture content of such material prior to exposure of said current,maintaining under vacuum a portion of said current of dehydrating gas towhich said particles of material are exposed, and regulating in part thedehydrating elfect of such gas upon the particles of material by varyingthe degree of vacuum to which such material is exposed, the vacuum beingvaried proportionately to the original moisture content of the materialprior to exposure to said current, the vacuum being relatively high whenthe initial moisture content of the material is high and relatively lowwhen the initial moisture content is low.

14. A method of dehydration according to claim 13 in which the currentof dehydrating gas is established by drawing atmospheric air through afurnace to be heated and commingled with flue gas and the delivery ofthe particles of material through the current includes the step ofrepeatedly showering across said current particles of material to bedehydrated whereby said material will be advanced by said current whilethe gas and air are evaporating moisture therefrom, and increasing anddecreasing the vacuum and the temperature of air and gas of said currentin accordance with increase and decrease of wetness of the material tobe dehydrated.

15. The method recited in claim 14 in which the increase in vacuum ofthe air and gas to which. the material is exposed is effected bywithdrawing air and gas from said current at an increased rate andconcurrently restricting the admission of air to said current, wherebyfurther to decrease the rate at which the material will be advanced bythe current when the material is wet, the rate of air and gas withdrawalbeing decreased and the rate of air admission being increased when thematerial to be dehydrated is relatively more dry.

16. The method of claim 15 in which the rate of withdrawing air and gasfrom said current, the temperature of the air and gas in said current,and the rate of admitting air to said current are all controlled inproportion to the temperature of dehydrating air and gas which has actedupon said material in the dehydration thereof.

References Cited in the file of this patent UNITED STATES PATENTS1,460,764 Neilsen et a1 July 3, 1923 1,988,677 Arnold Jan. 22, 19352,143,505 Arnold Ian. 10, 1939 2,153,951 Barker Apr. 11, 1939 2,225,397Franks Dec. 17, 1940 2,266,292 Arnold Dec. 16, 1941 2,318,576 Arnold May11, 1943 2,334,949 ONeal et al Nov. 23, 1943 2,461,420 Hoenshell Feb. 8,1949 2,525,535 Erisman et al Oct. 10, 1950 2,602,594 Hesse July 8, 19522,608,768 Noel Sept. 2, 1952 2,633,390 Bush Mar. 31, 1953 2,708,503Arnold Mar. 17, 1955 2,792,293 Faubrose et a1 May 21, 1957

12. A METHOD OF DEHYDRATION WHICH COMPRISES THE STEPS OF EXPOSINGMATERIAL TO BE DEHYDRATED TO A DEHYDRATING GAS COMPRISING TO COMBINATIONOF FLUE GAS AND AMBIENT AIR, ESTABLISHING A CURRENT OF SUCH GAS,REPEATEDELY SHOWERING SUCH MATERIAL TRNASVERSELY OF THE CURRENT TO BEADVANCED BY THE CURRENT AND SUPPLYING ADDITIONAL MATERIAL TO SUCHCURRENT AT A RATE PROPORTIONED TO THE TEMPERATURE OF GAS WHICH HAS ACTEDON SUCH MATERIAL, INDREASING AND DECREASING THE SPEED AND TEMPERATURE OFSAID CURRENT OF DEHYDRATING GAS IN ACCORDANCE WITH THE INCREASE ANDDECREASE OF WETNESS OF THE MATERIAL TO BE DEHYDRATED, AND DECELERATINGSAID CURRENT IN PROPORTION TO THE RISE OF HUMIDITY IN TE AMIBENT AIRADMITTED THERETO.